试图打破 CardLayout

Question

我正在尝试将我的代码分成更小的类。我目前正在使用 CardLayout。第一类显示变量很好，但第二类没有显示任何东西。当我转到第二张卡时，我得到一个空白页。我确定原因是因为它们没有分成类。我是否需要在不同的类中设置 CardLayout 并让这两个共享？

头等舱

public  test1()
{
    mainCL.setLayout(c1);
    main1.setPreferredSize(new Dimension(800, 900));
    mainCL.add(main1,"1");
    main1.setBackground(Color.BLUE);
    main1.setLayout(null);
    main2.setLayout(null);
    btnNewButton.setBounds(254, 835, 117, 29);
    main1.add(btnNewButton);

    JComboBox comboBox = new JComboBox();
    comboBox.setBounds(189, 130, 244, 27);

    main1.add(comboBox);
    mainCL.add(main1,"1");
    mainCL.add(main2,"2");
    c1.show(mainCL, "1");

    frame.setBounds(100, 100, 450, 300);
    frame.getContentPane().add(mainCL);
    frame.setVisible(true);
    frame.pack();
    frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);

btnNewButton.addActionListener(new ActionListener() {
    public void actionPerformed( ActionEvent arg0) {
        c1.show(mainCL,"2");
    }
    });

}


public static void main(String[] args) {
    SwingUtilities.invokeLater(new Runnable(){
        public void run() {
            new ttt();
        }
    });
}

二等

public class test2 extends test1{

private final JButton btnNewButton1 = new JButton("drop");

test2(){

    JComboBox comboBox1 = new JComboBox();
    comboBox1.setBounds(189, 200, 244, 27);

    btnNewButton1.setBounds(254, 835, 117, 29);
    main2.add(comboBox1);
    main2.add(btnNewButton1);

}

编辑

抱歉之前的代码。我只是对此进行测试，所以我没有考虑命名约定。做了一些研究，我想我可能已经解决了我的问题。下面是我更新的代码。如果我有问题，请告诉我。谢谢！

头等舱

public  test1()
{
private JLabel label;
JFrame frame;
JPanel panelCont;
JPanel panelOne;
JButton btnOne;
JComboBox signD = new JComboBox();
CardLayout cards;
test2 panelTwo;

public test1() {
    frame = new JFrame("CardLayout in two classes test");
    panelCont = new JPanel();
    panelOne = new JPanel();
    panelOne.setPreferredSize(new Dimension(600, 600));
    cards = new CardLayout();
    panelTwo = new test2(cards, panelCont);
    label = new JLabel("Page 1");
    btnOne = new JButton("Switch");
    panelCont.setLayout(cards);
    panelOne.setBackground(Color.BLUE);
    panelCont.add(panelOne, "1");

    //GridBag
    GridBagConstraints gbc_label = new GridBagConstraints();       
    GridBagLayout gbl_panelOne = new GridBagLayout();
    GridBagConstraints gbc_signD = new GridBagConstraints();
    GridBagConstraints gbc_buttonOne = new GridBagConstraints();

    //Panel
    gbl_panelOne.columnWidths = new int[]{100,400,100};
    gbl_panelOne.rowHeights = new int[]{100,400,100};
    panelOne.setLayout(gbl_panelOne);

    //Label
    label.setFont(new Font("Avenir", Font.PLAIN, 35));        
    gbc_label.gridx = 1;
    gbc_label.gridy = 0;
    panelOne.add(label, gbc_label);

    //Dropdown
    signD.setPreferredSize(new Dimension(200, 27));                                                                                 
    signD.setCursor(Cursor.getPredefinedCursor(Cursor.HAND_CURSOR));
    signD.setModel(new DefaultComboBoxModel(new String[] {"Dropdown1", "Dropdown2"}));
    signD.setForeground(Color.DARK_GRAY);       
    gbc_signD.gridx = 1;
    gbc_signD.gridy = 1;
    panelOne.add(signD, gbc_signD);

    //Btn
    btnOne.setCursor(Cursor.getPredefinedCursor(Cursor.HAND_CURSOR));
    btnOne.setHorizontalTextPosition(SwingConstants.CENTER);       
    gbc_buttonOne.gridy = 2;
    gbc_buttonOne.insets = new Insets(0, 0, 20, 5);
    gbc_buttonOne.anchor = GridBagConstraints.SOUTH;
    gbc_buttonOne.gridx = 1;
    panelOne.add(btnOne, gbc_buttonOne);

    //ActionListener
    btnOne.addActionListener(new ActionListener() {
       public void actionPerformed(ActionEvent e) {
       cards.show(panelCont, "2");
       }
    });
    panelCont.add(panelTwo, "2");
    cards.show(panelCont, "1");

    //Frame
    frame.getContentPane().add(panelCont);
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    frame.pack();
    frame.setVisible(true);
}
}

二等

public class test2 extends JPanel{

  JButton btnTwo;
CardLayout layout;
JPanel panelCont;
JLabel label = new JLabel("Page 2");
JComboBox signD2 = new JComboBox();

public test2(final CardLayout layout, JPanel panelCont) {
    this.layout = layout;
    this.panelCont = panelCont;
    GridBagLayout gridBagLayout2 = new GridBagLayout();
    gridBagLayout2.columnWidths = new int[]{100,400,100};
    gridBagLayout2.rowHeights = new int[]{100,400,100};
    setLayout(gridBagLayout2);
    setBackground(Color.RED);
    btnTwo = new JButton("Back");

    //GridBag
    GridBagConstraints gbc_label = new GridBagConstraints();       
    GridBagConstraints gbc_signD = new GridBagConstraints();
    GridBagConstraints gbc_buttonTwo = new GridBagConstraints();

    //Label
    label.setFont(new Font("Avenir", Font.PLAIN, 35));        
    gbc_label.gridx = 1;
    gbc_label.gridy = 0;
    add(label, gbc_label);

    //Dropdown
    signD2.setPreferredSize(new Dimension(200, 27));                                                                                
    signD2.setCursor(Cursor.getPredefinedCursor(Cursor.HAND_CURSOR));
    signD2.setModel(new DefaultComboBoxModel(new String[] {"Dropdown3", "Dropdown4"}));
    signD2.setForeground(Color.DARK_GRAY);      
    gbc_signD.gridx = 1;
    gbc_signD.gridy = 1;
    add(signD2, gbc_signD);

    //btn
    btnTwo.setCursor(Cursor.getPredefinedCursor(Cursor.HAND_CURSOR));
    btnTwo.setHorizontalTextPosition(SwingConstants.CENTER);       
    gbc_buttonTwo.gridy = 2;
    gbc_buttonTwo.insets = new Insets(0, 0, 20, 5);
    gbc_buttonTwo.anchor = GridBagConstraints.SOUTH;
    gbc_buttonTwo.gridx = 1;
    add(btnTwo, gbc_buttonTwo);

    btnTwo.addActionListener(new ActionListener() {
        public void actionPerformed(ActionEvent e) {
            layout.show(panelCont, "1");
        }
    });

}

}

主要

public class main {

public static void main(String[] args) {
    SwingUtilities.invokeLater(new Runnable() {
        public void run() {
            new test1();
        }
    });
}}

Answer 1

我不确定您的目标是什么，是什么促使您提出这个问题，但假设您正在尝试重构代码以允许您创建更小且更易于管理的类，那么您不应该这样做就像你在组合更有意义的情况下滥用继承一样。相反，我建议您：

• 为在卡片布局使用容器中交换的 JPanel 卡片创建单独的类
• 创建一个或多个单独的类来帮助控制卡片交换，如果你愿意的话，一个卡片交换“引擎”
• 谨慎且有充分理由的继承，主要是如果您想以某种方式改变类的固有行为，例如 JPanel 的绘画

您的代码和您的问题的其他问题：

• 没有你在哪里创建 test1 或 test2 实例，而是似乎创建了一个完全不同的类的实例，ttt。这和您的代码缺少声明的变量，使我们难以重现您的问题以查看您可能做错了什么。据我们所知，您可能没有创建或使用 test2 实例。
• 您应该避免使用空布局和使用setBounds(...) 来放置组件，因为这会导致非常不灵活的 GUI，虽然它们在一个平台上看起来不错，但在大多数其他平台或屏幕分辨率上看起来很糟糕，而且很难更新和维护。
• 顺便说一句，你会想学习和使用Java naming conventions。变量名应全部以小写字母开头，而类名应以大写字母开头。学习这一点并遵循这一点将使我们能够更好地理解您的代码，并使您能够更好地理解其他人的代码。

例如，请参阅下面的代码。请注意，它的编写目的是可以将所有内容直接复制并粘贴到 IDE 中，因为只有一个类 CardExample，即具有 main 方法的类，是公共的并且具有所有导入：

import java.awt.BorderLayout;
import java.awt.CardLayout;
import java.awt.Color;
import java.awt.Component;
import java.awt.Font;
import java.awt.GradientPaint;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.GridBagLayout;
import java.awt.Paint;
import java.awt.event.*;
import java.util.ArrayList;
import java.util.List;
import javax.swing.*;

public class CardExample {
    private static void createAndShowGui() {
        CardExampleMain cardUser = new CardExampleMain();

        JFrame frame = new JFrame("Card Example");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.getContentPane().add(cardUser.getMainPanel());
        frame.pack();
        frame.setLocationRelativeTo(null);
        frame.setVisible(true);
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(() -> createAndShowGui());
    }
}

class CardExampleMain {
    private JPanel mainPanel = new JPanel();
    private CardUser cardUser = new CardUser();
    private Card1 card1 = new Card1(cardUser);
    private Card2 card2 = new Card2(cardUser);
    private Card3 card3 = new Card3(cardUser);
    private JComboBox<String> cardKeyBox;

    public CardExampleMain() {
        cardUser.addCard(card1, card1.getName());
        cardUser.addCard(card2, card2.getName());
        cardUser.addCard(card3, card3.getName());

        int itemsSize = cardUser.getKeys().size();
        String[] items = cardUser.getKeys().toArray(new String[itemsSize]);
        cardKeyBox = new JComboBox<>(items);
        cardKeyBox.setSelectedIndex(-1);
        cardKeyBox.addActionListener(e -> cardUser.show(cardKeyBox.getSelectedItem().toString()));

        JPanel topPanel = new JPanel();
        topPanel.setBorder(BorderFactory.createEtchedBorder());
        topPanel.add(new JLabel("Select Card:"));
        topPanel.add(cardKeyBox);

        mainPanel.setLayout(new BorderLayout());
        mainPanel.add(cardUser.getMainPanel());
        mainPanel.add(topPanel, BorderLayout.PAGE_START);
    }

    public JPanel getMainPanel() {
        return mainPanel;
    }

}

class CardUser {
    private CardLayout cardLayout = new CardLayout();
    private JPanel mainPanel = new JPanel(cardLayout);
    private List<String> keys = new ArrayList<>();

    public JPanel getMainPanel() {
        return mainPanel;
    }

    public void addCard(Component component, String key) {
        mainPanel.add(component, key);
        keys.add(key);
    }

    public void show(String key) {
        cardLayout.show(mainPanel, key);
    }

    public void next() {
        cardLayout.next(mainPanel);
    }

    public void previous() {
        cardLayout.previous(mainPanel);
    }

    public List<String> getKeys() {
        return keys;
    }
}

@SuppressWarnings("serial")
abstract class CardPanel extends JPanel {
    private static final int EB_GAP = 5;
    protected CardUser cardUser;
    protected Action nextAction;
    protected Action previousAction;
    protected Action showAction;

    public CardPanel(CardUser cardUser) {
        this.cardUser = cardUser;

        nextAction = new CardAction("Next", KeyEvent.VK_N, e -> cardUser.next());
        previousAction = new CardAction("Previous", KeyEvent.VK_P, e -> cardUser.previous());

        setBorder(BorderFactory.createEmptyBorder(EB_GAP, EB_GAP, EB_GAP, EB_GAP));
        setLayout(new BorderLayout());

        JPanel buttonPanel = new JPanel();
        buttonPanel.setOpaque(false);
        buttonPanel.add(new JButton(previousAction));
        buttonPanel.add(new JButton(nextAction));

        add(buttonPanel, BorderLayout.PAGE_END);

    }
}

@SuppressWarnings("serial")
class CardAction extends AbstractAction {
    private ActionListener listener;

    public CardAction(String name, int mnemonic, ActionListener listener) {
        super(name);
        putValue(MNEMONIC_KEY, mnemonic);
        this.listener = listener;
    }

    @Override
    public void actionPerformed(ActionEvent e) {
        listener.actionPerformed(e);
    }
}

@SuppressWarnings("serial")
class Card1 extends CardPanel {
    public static final String NAME = "Card 1";
    private static final Color COLOR_1 = Color.PINK;
    private static final Color COLOR_2 = new Color(150, 150, 255);
    private static final float WDTH = 20f;
    private static final int LBL_GAP = 40;

    public Card1(CardUser cardUser) {
        super(cardUser);
        setName(NAME);
        JLabel label = new JLabel(NAME);
        label.setFont(label.getFont().deriveFont(Font.BOLD, 128));
        label.setBorder(BorderFactory.createEmptyBorder(LBL_GAP, LBL_GAP, LBL_GAP, LBL_GAP));

        add(label);
    }

    @Override
    protected void paintComponent(Graphics g) {
        super.paintComponent(g);
        Graphics2D g2 = (Graphics2D) g;
        Paint paint = new GradientPaint(0f, 0f, COLOR_1, WDTH, WDTH, COLOR_2, true);
        g2.setPaint(paint);
        g2.fillRect(0, 0, getWidth(), getHeight());
    }
}

@SuppressWarnings("serial")
class Card2 extends CardPanel {
    public static final String NAME = "Card 2";
    private static final Color COLOR_1 = Color.BLACK;
    private static final Color COLOR_2 = Color.BLUE;
    private static final Color LABEL_FG = Color.LIGHT_GRAY;
    private static final String[] DATA = {"Monday", "Tuesday", "Wednesday", "Thursday", "Friday"};
    private JLabel label = new JLabel("Card 2", SwingConstants.CENTER);
    private JComboBox<String> comboBox = new JComboBox<>(DATA);

    public Card2(CardUser cardUser) {
        super(cardUser);
        setName(NAME);
        label.setForeground(LABEL_FG);

        JPanel centralPanel = new JPanel(new GridBagLayout());
        centralPanel.setOpaque(false);
        centralPanel.add(comboBox);

        add(label, BorderLayout.PAGE_START);
        add(centralPanel);
    }

    @Override
    protected void paintComponent(Graphics g) {
        super.paintComponent(g);
        Graphics2D g2 = (Graphics2D) g;
        Paint paint = new GradientPaint(0f, 0f, COLOR_1, getWidth(), getHeight(), COLOR_2, false);
        g2.setPaint(paint);
        g2.fillRect(0, 0, getWidth(), getHeight());
    }    
}

@SuppressWarnings("serial")
class Card3 extends CardPanel {
    public static final String NAME = "Card 3";

    public Card3(CardUser cardUser) {
        super(cardUser);
        setName(NAME);
        add(new JLabel(NAME, SwingConstants.CENTER));
        // TODO put more components in here
    }

}